The head rest device is an important element for keeping an occupant seated in a vehicle seat in a comfortable position by supporting the occupant's head. The head rest device installed on the central seat of the vehicle rear seats is usually foldable downward while no one is seated in the central seat to give a wide rear field of view to the driver or a passenger seated in the front seat.
An example of a known head rest device for a rear seat is disclosed in Japanese Published Patent Application No. 1(1989)-164310. This known head rest device is designed to be folded downwardly in a rearward direction by operating an element biased by a spring force for releasing a locking mechanism.
Another example of a known head rest device of this type is disclosed in Japanese Published Utility Model Application No. 62(1987)-111453. The head rest device described in this publication is pushed down or pulled up for effecting disengagement or engagement of a latch and pawl mechanism.
These conventional head rest devices are constructed of many components, and it is difficult to design them with a proper adjusting spring force for keeping the head rest in the folded position upon encountering an accidental force.
In light of the foregoing, a need exists for a head rest device that is not susceptible to the disadvantages and drawbacks pointed out above.